With gradually increasing applications of slow neutron detection and imaging technology in homeland security, material monitoring, slow neutron scattering source measurement and the like, requirements on slow neutron detectors are gradually increased. However, widely used 3He gas is unable to meet a growing demand for use. Different types of new slow neutron detectors have been developed for replacement of the 3He, including a gas slow neutron detector, a scintillator slow neutron detector, a semiconductor slow neutron detector, and so on.
For a slow neutron detector, a slow neutron converter is one of important structures. There is no charge in a slow neutron itself, and except for a few slow neutron sensitive nuclides such as 6Li, 10B, Gd, the slow neutron and other substances have relatively small reaction cross-sections, an intuitive effect is thus that the slow neutron is difficult to be directly detected. The slow neutron converter has plenty of slow neutron sensitive nuclides therein, and slow neutrons can be converted into charged particles by nuclear reactions. The detector may measure energy and position information of these charged particles more conveniently, and may in turn obtain relevant physical information of the incident slow neutrons.
In design of the gas slow neutron detector, there may be various types of slow neutron converters and slow neutron detectors, such as a gas slow neutron detector based on a cylindrical proportional detector array, a gas slow neutron detector based on plane-parallel ionization chamber stacking, depending on different basic detectors being used.
In the gas slow neutron detector based on the cylindrical proportional detector array, the most basic slow neutron detection unit is a cylindrical proportional detector, and each unit has an independent anode wire and a signal collection and processing system, typically, e.g., an array of “straw-tube” slow neutron detectors. However, a slow neutron sensitive area of the detector and slow neutron detection efficiency are roughly proportional to a square of the number of the cylindrical proportional detectors. There will be a great amount of work in installation and maintenance of a large number of anode wires in the whole system, and difference in detection efficiencies of various slow neutron detection units also adversely affects overall performance of the system.
In the gas slow neutron detector based on plane-parallel ionization chamber stacking, the most basic slow neutron detection unit is a plane-parallel ionization chamber, and each ionization chamber has an independent two-dimensional signal readout system, typically, e.g., a Gd-GEM slow neutron detector. However, the slow neutron detection efficiency of a single layer of plane-parallel ionization chamber is relatively low, and certain methods, such as multi-stacking or slow neutron grazing-incidence, are required to improve the overall efficiency of slow neutron detection. However, it will bring a great pressure on the overall signal readout processing, and is inconvenient to achieve slow neutron detection in a large area.